1. Field of the Invention
The present invention relates to procedures and devices for treating problems with the spine and, in particular, to procedures and devices for relieving pressure on the spinal cord.
2. Background Information
The spinal cord and nerve roots in the neck are surrounded and protected by the cervical vertebrae. These bones have an opening called the spinal canal through which the spinal cord passes. Ligaments and blood vessels are also present in the spinal canal. The nerve roots start at the spinal cord and pass through an opening between the vertebrae called the intervertebral foramen (or neural foramen). From there, the nerves extend to other parts of the body. It can thus be appreciated that any compromise to or trouble with the spine can cause various medical problems.
One of these problems is known as spinal stenosis. Spinal stenosis is a condition where there is narrowing of the spinal canal (and often the neural foramen), which causes compression of the spinal cord and/or nerve roots. This narrowing is caused by numerous factors including bone spurs, degeneration of the intervertebral disks and facet joints, and thickening of the ligaments. Among the symptoms spinal stenosis can produce are pain and/or numbness in the arms, clumsiness of the hands, and gait disturbances. The spine may also undergo other compression problems. If left untreated, such problems can lead to a loss in mobility and/or permanent physical damage.
One manner of treating spinal stenosis and other such spinal compression problems is to perform surgery. One prior art surgical procedure is known as a laminectomy. In a laminectomy, pressure against the spinal cord is relieved by removing the spinous process and lamina associated with an affected vertebra. With the posterior portion of the vertebra gone, the spinal cord is thus exposed. Since a laminectomy leaves the spinal cord exposed and removes a substantial portion of the posterior portion of one or more vertebra, various surgical alternatives have been sought.
One such alternative technique or procedure for the decompression of the spine, and especially the cervical spine, is a laminoplasty. In a laminoplasty, the spinal canal is expanded by repositioning the lamina rather than removing it completely, as in a laminectomy. With a laminoplasty, decompression is provided while maintaining the stabilizing effects of the posterior portion of the vertebra through retention of a portion of the posterior portion of the vertebra. The advantage of a laminoplasty is that it increases the size of the spinal canal but leaves a posterior portion that helps keep the spine stable.
In a laminoplasty, one side of a lamina is cut through while the other side of the lamina is grooved to create a “hinged” or “swinging” flap or door of bone. The lamina bone flap is then opened (thereby enlarging the spinal canal) to relieve pressure on the spinal cord. In the typical laminoplasty technique, a wedge or the like is placed between the free side of the lamina and the cut vertebra portion. A plate is then attached to the wedge, the lamina bone flap and the cut vertebra in order to fix the position of the lamina bone flap and the enlarged spinal canal.
The above laminoplasty approach, however, has various drawbacks. For instance, the pre-defined geometry of laminoplasty wedges can create the need for in-situ contouring. Additionally, pre-bent laminoplasty plates and/or other laminoplasty components having pre-defined configurations can add numerous iterations to the installation procedure. As is well known, the longer and more complicated the procedure, the greater the likelihood for problems.
In view of the above, it is apparent that there exists a need for a more versatile laminoplasty implant/implant system.
Additionally, it is apparent that there exists a need for a laminoplasty implant/implant system that provides a better fit with existing anatomies.
Moreover, it is apparent that there exists a need for a laminoplasty implant/implant system that provides for less in-situ contouring and fewer implant iterations.